Re: Towards a classification system for uses of the Private Use Area

From: Doug Ewell (
Date: Fri Apr 26 2002 - 11:50:15 EDT

Michael Everson <> wrote:

> The Private Use Area is not to be classified. Anyone anywhere can use
> any of its code points for anything.

Furthermore, even if William's scheme is intended to be a semi-private
"convention" rather than an official part of Unicode -- much like
Michael's (and John Cowan's) own ConScript Unicode Registry -- it seems
unlikely that an elaborate indexing scheme such as the one William
proposes would gain much of a following. Vendors have only recently
started to implement surrogates properly, and still balk at decoding
SCSU (which is easy; it's the encoding part that gets complex). And
these official Unicode mechanisms are simple compared to William's "hex
point" indexing scheme.

Additionally, it is VERY important to repeat -- probably more important
than anything else in this discussion -- that there is no automatic path
to "promotion" of any private-use character to full Unicode status.
Every character and script that is encoded in Unicode must undergo the
same scrutiny, regardless of how (or whether) it may have been encoded
in the past. That goes for Deseret and Shavian (accepted) as well as
Klingon and Aiha (not accepted), all of which were encoded in ConScript
but none of which were automatically "promoted" on that basis alone.

There are two full Private Use planes, 131,068 code points in all (not
counting the four noncharacters), certainly enough for any private-use
implementation that would be envisioned as benefiting from William's
proposal, and a lot easier to implement (and thus more likely to be
used). My suggestion to William is that if he envisions a potentially
widespread use for the PUA, he may consider creating a ConScript-like
registry for the upper planes. That would be just as effective and much

Apart from font vendors who use the PUA for presentation forms within
the font, what current practices exist for using the PUA? I mentioned
ConScript; how popular is its use? Are there any other commonly used
practices or conventions? Apple has blocked out a code point for APPLE
SIGN, and somebody (sorry, don't remember the name) mentioned a
Microsoft convention of a subarea for symbols or dingbats. Maybe a
discussion along these lines can reveal the true nature of PUA use and
help William redirect his considerable energy toward a more practical

-Doug Ewell
 Fullerton, California

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